This document discusses web services and how they can be created in ASP.NET using two primary models - the ASP.NET (.asmx) model and the Windows Communication Foundation (WCF) model. It provides details on how to define service contracts, implement and host services, and consume services from a client application for both models. The key aspects covered include defining endpoints, bindings, and contracts as well as attributes used for services, operations, data contracts, and more.

2.  There are things applications need very often. So why make
these over and over again?
 Web services can offer application-components like:
currency conversion, weather reports, or even language
translation as services.
 Unlike traditional client/server models, such as a Web
server/Web page system, Web services do not provide the
user with a GUI.
 Web services instead share business logic, data and
processes through a programmatic interface across a
network.
 Developers can then add the Web service to a GUI (such as a
Web page or an executable program) to offer specific
functionality to users.

3. There are two primary ways to create services
in ASP.NET.
 Web services based on the ASP.NET (.asmx)
model.
 Microsoft Windows Communication
Foundation (WCF) model

4. This is a familiar ASP.NET programming
experience for services that are meant to be
exclusively bound to Hypertext Transfer
Protocol (HTTP) and hosted by Microsoft
Internet Information Services (IIS) and
ASP.NET.

5.  The term Web services describes a standardized way of
integrating Web-based applications using the
XML, SOAP, WSDL and UDDI open standards over an
Internet protocol backbone.
 XML is used to tag the data, SOAP is used to transfer
the data, WSDL is used for describing the services
available and UDDI is used for listing what services are
available.
 Used primarily as a means for businesses to
communicate with each other and with clients, Web
services allow organizations to communicate data
without intimate knowledge of each other's IT systems

6. SOAP, originally defined as Simple Object Access
Protocol, is a protocol specification for exchanging
structured information in the implementation of Web
Services in computer networks.
It relies on Extensible Markup Language (XML) for its
message format, and usually relies on other
Application Layer protocols, most notably Hypertext
Transfer Protocol (HTTP) and Simple Mail Transfer
Protocol (SMTP), for message negotiation and
transmission.

7.  WSDL stands for Web Services Description
Language
 WSDL is an XML-based language for locating
and describing Web services.
 An XML-formatted language used to describe a
Web service's capabilities as collections of
communication endpoints capable of
exchanging messages.
 WSDL is an integral part of UDDI, an XML-
based worldwide business registry.

8. ASP.NET wrap the web service code as a proxy object. This object will
know how to expose your Web service. This includes deserializing SOAP
requests, executing your .NET Framework code, and serializing your
response to be sent back to the requesting client as a SOAP message.

9.  An ASP.NET XML Web service is a class you
write that inherits from the class System.Web
.Services.WebService.
 Create a Web service project through the Add
New Project ->ASP.NET Web Service application.
 This generates a separate project for your Web
service application that has a structure similar to
a Web site. This includes a folder for App_Data, a
Web.config file, and related elements.

10.  Like a Web page, Web services are exposed through
Uniform Resource Locators (URLs).
 This means your domain name followed by a page
name, as in http://MyDomain/MyService.asmx.
 Web service like a class that only exposes methods. Each
Web service can expose multiple methods.
 The page for an XML Web service is defined by the .asmx
file. This file is nothing more than a simple text file that is
used as a pointer to the code of your Web service.
 @ WebService directive points to the actual code for the Web
service.

11.  This class can be used to provide information about
your Web service. This information is used by clients
that wish to reference the Web service.
 You can provide both a namespace and a description
of your Web service by applying the WebService
attribute and parameters to your class.
 The description parameter is simply text you write to
identify the high-level intent of your Web service.
 The namespace parameter sets the namespace of your
Web service. This should be a domain name under
your control. Visual Studio uses the tempuri.org
namespace as filler until you define your actual namespace.

12.  You apply this attribute to any public method in your
Web service class you wish to expose as part of your
service.
 The WebMethod attribute class has a number of
constructors used for various groups of parameter
values.
1. enableSessionState
2. transactionOption
3. cacheDuration
4. bufferResponse
 You can also use the Serializable attribute class to tag
class outside your Web service. This ensures any public
members of the class can be serialized by ASP.NET.

13.  The first step is setting a Web reference from your
Web site to the given service. You do this by
right-clicking your project file and choosing Set
Web Reference.
 This opens the Add Web Reference dialog box.
Here, you define the URL of your service, select
the given service (.asmx file), and set a name for
the reference. This name will be used by the
generated proxy class to define the namespace for
accessing your service.

14.  This model allows developers to write services
that can be configured to work with a variety of
hosts, protocols, and clients. For example, you
might want to write a service that is accessed
over Transmission Control Protocol (TCP)
instead of HTTP.
 If that same service code needed to be called
over both HTTP and TCP, you had to write and
host it twice. This is one of the many problems
WCF is meant to solve.

15.  WCF is a unifying programming model.
 It is meant to define a singular way for writing
services and thereby unify things like Web services
(.asmx), .NET Remoting, Message Queue
(MSMQ), Enterprise Services (COM+), and Web
Services Enhancements (WSE).
 It does not replace these technologies on an
individual basis. Instead, it provides a single
programming model that you can use to take
advantage of all of these items at once.
 With WCF, you can create a single service that can be
exposed as HTTP, TCP, named pipes, and so on.
 You also have multiple hosting options.

17.  WCF Service is a program that exposes a
collection of Endpoints.
 Each Endpoint is a portal for communicating
with the world.
 All the WCF communications are take place
through end point. End point consists of three
components.
 Address
 Binding
 Contract

18.  Basically URL, specifies where this WCF
service is hosted .
 Client will use this url to connect to the service.
 http://localhost:8090/MyService/SimpleCalcu
lator.svc

19.  Binding will describes how client will communicate
with service. There are different protocols available for
the WCF to communicate to the Client. You can
mention the protocol type based on your requirements.
 The following table gives some list of protocols
supported by WCF binding.

20.  Collection of operation that specifies what the
endpoint will communicate with outside world.
 Usually name of the Interface will be mentioned in
the Contract, so the client application will be aware
of the operations which are exposed to the client.
 There are multiple contract types in
WCF, including service contract, operation
contract, message contract, fault contract (for error
handling), and data contract.
 These contracts work together to indicate to the
client code consuming the WCF service how it
should define communication messages

23.  Creating and consuming WCF services follow a
standard set of programming tasks. You follow
these steps every time you wish to create and
consume a new WCF service:
1. Define the service contract.
2. Implement (or write) the service contract.
3. Configure a service endpoint(s).
4. Host the service in an application.
5. Reference and call the service from a client
application.

24.  In WCF programming, you first define an
interface and decorate that interface with a
number of attributes.
 These WCF attribute classes are found in the
System.ServiceModel namespace.
 These attribute classes are used to define the
details of the contract that your service will
have with calling clients.

25.  ServiceContract : The ServiceContract attribute class has
parameters for setting things like whether the service
requires a session (SessionMode), the namespace, the
name of the contract, the return contract on a two-way
contract (CallbackContract), and more.
 OperationContract : attribute class to set things like
whether the contract does not return a reply
(IsOneWay), the message-level security (ProtectionLevel), or
whether the method supports asynchronous calls
(AsyncPattern).
 DataContract : The DataContract attribute class is used to
mark types you write (classes, enumerations, structures)
 DataMembers : The DataMember attribute class is used to
mark individual fields and properties that you want to
serialize. You use this class in conjunction with the
Data-Contract class.

26.  Visual Studio and ASP.NET define the WCF Service
Application project template. This template defines a
Web project that serves to host the WCF service. This
project contains a reference to
System.ServiceModel.dll, which contains the WCF classes.
Creating a new instance of this project template will also
generate a default service (Service1.svc) and a related
contract file IService1.vb or .cs).

27. Finally, a WCF Service application is automatically configured
to be hosted in IIS and expose a standard HTTP endpoint. This
information can be found inside the <system.servicemodel>
section of the Web.config file.
<system.serviceModel>
<services>
<service name="NorthwindServices.Service1"
behaviorConfiguration="NorthwindServices.Service1Behavior">
<endpoint address="" binding="wsHttpBinding"
contract="NorthwindServices.IService1">
<identity>
<dns value="localhost"/>
</identity>
</endpoint>
<endpoint address="mex" binding="mexHttpBinding"
contract="IMetadataExchange"/>
</service>
</services>

28. <behaviors>
<serviceBehaviors>
<behavior name="NorthwindServices.Service1Behavior">
<!-- to avoid disclosing metadata information, set the value below
to false
and remove the metadata endpoint above before deployment -->
<serviceMetadata httpGetEnabled="true"/>
<!-- To receive exception details in faults for debugging
purposes, set the
value below to true. Set to false before deployment to avoid
disclosing
exception information -->
<serviceDebug includeExceptionDetailInFaults="false"/>
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>